MarkDown Hover text from a custom Langauge Server (LSP)

Question

MarkDown Hover text from a custom Langauge Server (LSP)

Sajith 86

I develop an extension in Visual Studio that implements a Language Server (LSP) and support Hover (textDocument/hover) on keywords in editor. I was using MarkupKind.Markdown for the Hover Contents type.

					hover = new Hover
					{
						Contents = new MarkupContent
						{
							Kind = MarkupKind.Markdown,
							Value = hoverText
						}
					};

This was working fine earlier in both VS2022 and VS2026. But doesn't work with VS2026 update - 18.9.1.

Setting Kind to 'MarkupKind.PlainText' works fine. Is this expected with VS2026 - 18.9.1 ?

Is only PlainText supported, doesn't Visual Studio support Markdown text as Hover from a custom Language Server textDocument/hover request?
I want to show rich text hover as in C#
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Is this possible from a custom Language Server(LSP)? Please guide how to implement this.

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Answer 1

Hi @Sajith ,

The Hover construction you shared is a valid way to supply MarkupContent; Microsoft’s API documentation explicitly lists it as an accepted type for Hover.Contents. However, this alone does not establish Markdown rendering support in a particular Visual Studio client. learn.microsoft.com

Since you reported that the same implementation worked before updating to 18.9.1, I would investigate a possible client-side change rather than immediately classify this as expected behavior. This is not yet a confirmed regression. learn.microsoft.com

Please compare capabilities.textDocument.hover.contentFormat in the client’s initialize request between the working and affected versions. This capability identifies the supported markup formats. learn.microsoft.com

For troubleshooting, please:

Test a minimal value such as "**Hover test**\n\nSimple description.".
Capture the actual serialized hover response.
If the client advertises only plaintext, use plain-text content as a compatibility fallback.
If it advertises Markdown but the minimal response fails only in the affected version, submit a Report a Problem with the reproduction and LSP traces. learn.microsoft.com

For a tooltip with custom icons, classified text, and interactive links like the screenshot, consider a Visual Studio-side Async Quick Info provider. Microsoft provides an official sample; this is an editor-extension approach rather than a server-only Markdown change.

Note: This is not an official Microsoft Learn document, however it contains useful information that you may refer to. github.com

If you found my response helpful or informative, I would greatly appreciate it if you could follow this guide for your confirmation.

Thank you.